An unbeatable ground game, a timely endorsement by former President Bill Clinton and voter backlash against a negative ad campaign.

By most accounts, that’s what it took to transform Tuesday’s battle between two longtime friends and Democratic congressional veterans — U.S. Reps. Bill Pascrell and Steve Rothman — from a nail-biter into a blowout. Pascrell won with an unexpectedly large margin of more than 60 percent of the vote.

"You take my hometown of Paterson where I’ve lived all my life," Pascrell said Wednesday, hours after receiving a congratulatory call from President Obama. "Once those folks get energized, stay out of their way."

In the end, Pascrell received 30,000 votes to Rothman’s 19,000 — a lopsided margin owing largely to Pascrell’s native Passaic County, especially Paterson. Though smaller than Rothman’s base in Bergen County, Passaic County vastly outperformed its neighbor.

"We thought we were in a very tight race," Paul Swibinski, a Rothman strategist, said. "We did get over 70 percent of the vote in Bergen County and in Hudson County. But the numbers out of Passaic County were just remarkable."

John Currie, the Democratic chairman in Passaic County, said his organization "had an operation like that you wouldn’t believe."

Currie said 12,000 new voters were registered, and dozens of vans were made available to ferry them to the polls. In addition, he said a swarm of staff members knocked on doors and distributed campaign literature.

Still, what made the landslide more surprising was that initially Rothman was favored to win.

Voters were ultimately forced to decide between the two men after the state whittled its 13 congressional districts to 12 because of New Jersey’s slow population growth. In December, the axe fell on Rothman when his hometown of Fair Lawn was shifted to the Republican-leaning district of U.S. Rep. Scott Garrett (R-5th Dist.).

Rothman chose to move to Englewood — where he once was mayor — and take on Pascrell in the new 9th District. For his part, Pascrell saw his district splintered, and the majority of voters in his new one had been represented by Rothman.

Also, between Rothman’s narrow fundraising advantage and a historically low voter turnout in Paterson, the race was considered Rothman’s to lose.

Pascrell said his campaign’s early polls showed him trailing by 12 to 15 points. "We turned it around partly because of what we were doing," he said, "and partly because what he decided to do."

Although endorsements don’t usually count for much, Clinton’s did. First he endorsed Pascrell, calling him "the fighter we need to support President Obama," and last Friday he appeared at rally in Paterson.

"He gave them an endorsement and a great quote four weeks before Election Day," Swibinski said. "There’s nobody stronger than Clinton to deliver a message like that unless you have the president himself."

Rothman tried to counter Clinton’s support by showing off his close relationship with President Obama, whom he had supported in 2008 when every other Democrat congressman, including Pascrell, backed Hillary Rodham Clinton for the Democratic presidential nomination.

Obama’s top political advisor, David Axelrod, campaigned for Rothman. And the day Clinton rallied for Pascrell, Obama met with Rothman in the Oval Office and strolled with him in full view of reporters — though he stopped short of endorsing him and never set foot in the district during the campaign.

And then there were Rothman’s ads accusing Pascrell of siding with Republicans on such issues as immigration and partial-birth abortion.

Swibinski insisted the negative ads did not turn off voters, but Patrick Murray, a pollster at Monmouth University, disagreed. "This whole campaign was an example of exceptions to the rule," he said. "It was an example of where an endorsement actually did matter ... when negative campaigning actually increased turnout rather than decreased it."

Ultimately, Rothman may have fared better against the conservative Garrett.

As Currie put it: "If Rothman ran against Garrett, not only was the congressional committee chairman going to pour money into that election, but he would have had the help of all of us ... he would have had more good will."